The present invention is generally directed to guides, guide assemblies and/or guide mechanisms for use in conjunction with pluggable cartridges for inserting printed circuit cards into and for removing them from printed circuit boards. More particularly, the present invention is directed to an integral guide structure which provides a guiding, alignment and locking function. Even more particularly the present invention includes a cartridge which mates with the desired guide structure so that cartridges are firmly locked into position to permit a self-contained actuation mechanism within the cartridge to slidably move a printed circuit card within the cartridge so as to forcibly mate a card edge electrical connector to a matching printed circuit board mounted connector.
The past twenty-five or so years have seen the development of ever smaller electrical circuit components at the chip level. However, to take fullest advantage of achievements in electrical circuit miniaturization, one must package the resultant printed circuit cards containing these chips in an efficient manner. Clearly, the packaging of printed circuit cards in tight spaces is a direct logical extension of increasing chip level circuit densities. It should also be noted that the tight packaging of integrated circuit chips on printed circuit cards and the correspondingly dense packaging of the printed circuit cards is a design goal that is carried out for more than just the convenience of compactness. Compactness provides shorter distances between circuit components which, in turn, serves the very desirable goal of being able to operate the circuits effectively at higher frequencies, thus increasing the speed of numerous different forms of electrical systems, including but not limited to data processing systems.
Moreover, mainly for reasons associated with long-term system operation and reliability, it is likewise very desirable to be able to easily insert and remove these printed circuit cards even when they are disposed in very tight spaces. The insertion and removal operations are also provided as an important part of a xe2x80x9chot-pluggabilityxe2x80x9d function which is very desirable for xe2x80x9con the flyxe2x80x9d repairs, replacements, maintenance and upgrades.
With increased circuit density there has also been a concomitantly driven increase in the number of power, signal and control lines which require electrical connections to be made between printed circuit cards and printed circuit boards. This means that the electrical connectors that carry these various electrical circuits between the cards and the boards have been required to carry more and more separate individual connections. A significant consequence of the increase in the number of individual electrical connections, all of which require surety of contact, is the corresponding increase in the force needed to insert printed circuit connectors into mating printed circuit board sockets. This aspect provides special design considerations for self-contained cartridges that carry printed circuit cards which are meant to be inserted into printed circuit boards via actuating mechanisms contained within the cartridge itself.
The increase in the number of connections also poses other problems in the design of desirably compact packaging systems, particularly those designed for easy cartridge insertion and removal. In particular, the increased number of connections results in the use of connectors with an increased number of pins and socket holes. Since these structures are present in larger and larger numbers, the pin-and-socket connections (or the like) are themselves packed together with smaller and smaller distances between them. This aspect of the packaging problem brings along with it the problem of connecting pin alignment for the purpose of physically connecting oppositely disposed mating pins and socket holes. Alignment failure can severely and permanently damage both the printed circuit card and the printed circuit board into which the card is to be inserted.
Also of note is the fact that one of the principle purposes of the present invention is to provide cartridges which are capable of this self-contained insertion actuation function. Even more particularly, the present invention employs cartridges which are designed to have no physical contact with any external structure except the printed circuit board itself. This means that cartridges of the present invention do not require any form of actuation mechanism which relies upon external structures such as an enclosure, cabinet or frame or upon any form of adaptation provided in a surrounding cabinet, frame or enclosure. This also means that there are no frictional elements disposed between the printed circuit board and its surrounding structures. And this is turn implies that the entire printed circuit board may be inserted and removed as an integral, fully populated structure, that is, with a full set of printed circuit cards inserted (within cartridges). However, this desirable feature makes cartridge design more difficult in that there still must be provided some mechanism for resisting insertion forces, however, slight they may sometimes be.
Additionally, if the printed circuit board is itself intended to be inserted and removed with its complement of printed circuit cards in place, it should also be substantially rigid particularly in those circumstances in which the horizontal dimensions of the board are large with respect to its vertical height. If the printed circuit board is wide and long but thin, then insertion in particular can result in undesirable bending and flexing of the board which is commonly referred to as xe2x80x9coil canning.xe2x80x9d
As an additional constraint on packaging design, it should be appreciated that, with increased circuit density, there is also a concomitant increase in power density and heat dissipation. Accordingly, packaging designs should be fully compatible with those aspects of system design associated with cooling functions. Also, to whatever extent possible, packaging designs should be: economical to produce; function smoothly; require little or no maintenance; be producible from inexpensive, readily available materials; and be reliably operable over a large number of insertion and removal operation cycles.
Yet one other concern arises in electrical systems as circuit feature size shrinks, operating frequencies increase and packaging densities grow larger, namely, the generation of electromagnetic interference (EMI). Electronic circuit packaging designs should thus also be compatible with structures and configurations that are employed to prevent the leakage of electromagnetic interference. To whatever extent possible, packaging designs should also include structures which actually contribute positively to the containment of electromagnetic interference.
Furthermore, it is noted that whatever guide and locking mechanism is employed, it is ultimately placed on the printed circuit board which is intended for printed circuit card insertion (and later removal, as needed or desired). Accordingly, the guide should be compatible with printed circuit board function and, if possible, contribute to its structural rigidity to counteract the above-mentioned oil-canning effect.
It is also noted that the present discussion refers to printed circuit boards and printed circuit cards. As contemplated herein, the printed circuit board is the larger component into which at least one printed circuit card is inserted for purposes of electrical connection. The present invention places no specific limits on either the size of a printed circuit board or the size of a printed circuit card. In the most general situation, a circuit board will be populated with a plurality of printed circuit cards. That is, the printed board will have a number of printed circuit cards inserted therein. Accordingly, as used herein, the terms xe2x80x9cprinted circuit boardxe2x80x9d and xe2x80x9cprinted circuit cardxe2x80x9d are considered to be relative terms.
Accordingly, the present inventors are presented with the following sometimes competing packaging problems: connector pin alignment, cartridge alignment, rigid connection to a printed circuit board, circuit board oil canning, dense and close packaging, cooling, electromagnetic interference shielding, hot pluggability, the desire to provide an easy-to-load cartridge for carrying printed circuit cards, mechanisms requiring a mechanical advantage for insertion and removal of printed circuit cards, the removal of fully populated printed circuit boards and the insertion thereof, and means to provide a cooperative EMI shielding arrangement in a system which provides circuit board guide mechanisms which do not require physical contact with a surrounding enclosure or cabinet.
In accordance with a preferred embodiment of the present invention, a guide structure which is especially suited for insertion of self-contained pluggable printed circuit board cartridges comprises three major portions: a rear portion, a front portion and slot defining rungs extending between the front and rear portions. The rear portion includes at least one vertical tab with an alignment aperture in the tab. This aperture is meant to receive a corresponding alignment pin on the cartridge to be inserted. The guide structure also includes a forward portion which includes a step. The vertical portion of the step also includes at least one other alignment aperture. One or both of the alignment apertures also provides a locking function. There is also at least one pair of cartridge slot defining rungs extending from the rear portion to the forward portion with the pair of rungs being disposed on opposite sides of a matching pair of the alignment apertures, one of which is disposed in the vertical tab with the other aperture being disposed in the vertical step.
In preferred embodiments of the present invention, the guide structure is formed from a single sheet metal stamping. The rear portion preferably includes a channel which act as a stiffening rib both for the guide structure itself and for the printed circuit board on which it is mounted.
The present invention also includes a mating printed circuit card carrying pluggable cartridge which is intended for use with the above-described guide structure. A desirable pluggable cartridge intended for such use preferably comprises a rigid frame with a printed circuit card having a pluggable electrical connector being slidably disposed within the frame. A lever mechanism, disposed between the rigid frame and the printed circuit card is provided for slidably moving the printed circuit card relative to the frame. A guide pin is externally affixed to the frame and a locking pin is preferable affixed externally to the frame. Thus, the cartridge is guided into and locked into a mating printed circuit-board-level guide structure so that the lever mechanism may be actuated to cause the pluggable electrical connector on the printed circuit card to mate with a corresponding connector on the printed circuit board.
Accordingly, it is an object of the present invention to provide structures and mechanisms for densely package electronic circuit components while at the same time providing easy access and component replacement capabilities, especially for hot pluggability applications.
It is a further object of the present to provide a guide for use with cartridges containing pluggable printed circuit cards.
It is also an object of the present invention to provide a design for a cartridge guide which is easily and economically fabricatable in the form of a single sheet of stamped metal.
It is a still further object of the present invention to provide a board level docking mechanism which provides guide, alignment, locking and holding functions.
It is a further object of the present invention to provide a guide mechanism for printed circuit boards which also serves the function of providing an added degree of stiffness to the circuit board on which it is mounted.
It is still another object of the present invention to provide a board level cartridge guide mechanism which not only provides a certain level of electromagnetic interference shielding but which also cooperates with the inserted cartridge to meld together card level and board level shielding functions.
It is also another object of the present invention to provide a printed circuit card carrying cartridge which not only mates with but which also cooperatively interacts with a desirable board level guide mechanism.
It is a further object of the present invention to provide a printed circuit card carrying cartridge which is capable of providing flow through air cooling passages.
It is yet another object of the present invention to provide a docking cartridge which is fool proof and which does not require the use of tools.
It is a still further object of the present invention to facilitate the packaging of electronic circuit components in tight spaces.
It is also another object of the present invention to be able to provide electronic circuit packaging design structures which facilitate easy insertion and removal of printed circuit cards.
Lastly, but not limited hereto, it is an object of the present invention to facilitate packaging designs for increasingly dense, fast and powerful electronic systems.
The recitation herein of a list of desirable objects which are met by various embodiments of the present invention is not meant to imply or suggest that any or all of these objects are present as essential features, either individually or collectively, in the most general embodiment of the present invention or in any of its more specific embodiments.
The subject matter which is regarded as the invention is particularly pointed out and distinctly claimed in the concluding portion of the specification. The invention, however, both as to organization and method of practice, together with the further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings in which:
FIG. 1 is an isometric view illustrating a cartridge of the present invention being inserted into a guide of the present invention which is disposed on a rigid printed circuit board with the guide also operating as a printed circuit board stiffener for increased rigidity;
FIG. 2 is an isometric view similar to FIG. 1 but more particularly showing a cartridge in a position in which the cartridge, though not necessarily the printed circuit card, is fully inserted into a mating printed circuit board slot in which it is aligned and locked;
FIG. 3 is an isometric view of a guide of the present invention incorporating a plurality of guide slots and, as preferred, from a single sheet of stamped metal;
FIG. 4 is a detailed view of a portion of the guide shown in FIG. 3;
FIG. 5 is an isometric view showing a detailed view of the portion a FIG. 2 which specifically relates to the function of the guide pin;
FIG. 6 is a side elevation view illustrating the locations of the locking and guide pin structures particularly as they relate to their positions relative to the cartridge and the board level guide structure;
FIG. 7 is a side elevation view illustrating the interior construction of a cartridge of the present invention so as to particularly show the preferred actuating lever mechanism, the slidable mounting for the printed circuit card and the edge connector;
FIG. 8 is an isometric view illustrating the desired shape and arrangement for a snap-in locking pin;
FIG. 9A is a top view of an EMI shield spring employable in conjunction with the EMI shield system of the present invention; and
FIG. 9B is a side elevation view of the spring shown in FIG. 9A.